The present invention relates to a vehicle seats, in particular to hydraulic or fluid powered adjustable automotive vehicle seats.
In order to comfortably accommodate various sizes and shapes of occupants vehicle seats are generally provided with various adjustment mechanisms to adjust the position of the seat within the vehicle and/or move various movable portions of the seat.
Typically vehicle seats are provided with fore and aft adjustment, and the seat back is pivotally mounted to a seat bottom cushion such that the angle of the seat back to the bottom cushion of the seat can be adjusted. Other adjustment and adjustment mechanisms may also be provided to for example adjust the height of the vehicle seat, angle and tilt of the seat bottom cushion, position of the headrest, and/or the lumber support etc.
The seat adjustment mechanisms may be manually operable and mechanically locked in place, or increasingly some or all may be power operated. Conventionally such power operated adjustment mechanisms comprise separate electric motors mounted within the seat and driving each adjustment mechanism through suitable gearing. The individual motors are controlled via switches operable by the seat occupant.
Alternatively hydraulic or fluid powered seat adjustment mechanisms have been proposed instead of the electric powered systems. Indeed the earliest of such proposals date back a number of years. A distinction should however be drawn between hydraulic or fluid powered adjustment systems, and the more basic and simple and hydraulic or pneumatic damper arrangements.
In hydraulic or fluid powered seat adjustment arrangements pressurised fluid, provided from a pump, is supplied via a control valve arrangement to piston/cylinder actuators. These actuators move and adjust the position of the seat or portions of the seat to be adjusted. An example of a hydraulic powered seat adjustment system incorporating a hydraulic actuator is described in U.S. Pat. No. 5,435,625.
Such powered hydraulic seat adjustment systems offer smooth and almost infinitely variable adjustment and locking of the position of the seat. This can be contrasted with the incremental locking provided by conventional mechanical arrangements. Hydraulically powered arrangements also offer the prospect of extremely quiet, near silent, operation, without the noisy mechanical gearing. In spite of these, and other, advantages hydraulic actuators for vehicle seat adjustment have not been adopted for widespread automotive use.
Specifically a major problem with such hydraulic systems is the cost and perceived complexity of the systems. In particular the complexity of the control valve, control arrangements, and ancillary elements in previous systems has also made the systems impractical for automotive adoption, and/or rendered the previously proposed arrangements unsuitable for practical use.
It is therefore desirable to provide an improved hydraulically powered automotive vehicle seat adjustment system, and in particular a hydraulic vehicle seat adjustment control valve arrangement for such a system, which addresses the above described problems and/or which offers improvements generally.